A wide variety of therapeutic procedures have been developed to intervene in patients with coronary artery disease. Whether the intervention is intended to increase lumen size by dilating the artery or to decrease atheroma mass by laser ablation, mechanical atherectomy, or by lowering serum cholesterol, it will be important to quantitate atherosclerotic plaque volume before and after treatment. The purpose of the proposed study is to further our knowledge about the structural changes of arterial remodeling that occur during and following interventional procedures performed to increase the lumen of atherosclerotic arteries. This evaluation will be accomplished using a new method of imaging arteries in vivo with an intravascular ultrasound imaging catheter. The interventions that will be studied are balloon dilatation, atherectomy, laser ablation, and a cholesterol drug intervention trial. Studies will be performed in vitro to evaluate the accuracy and reproducibility of the imaging catheter for obtaining quantitative information about lumen cross-sectional area, and atherosclerotic plaque thickness and volume. In vivo animal studies will be used to assess its function and safety. Human clinical studies will be undertaken to correlate the findings of the intravascular ultrasound images with angiography. In addition, the ultrasound imaging catheter will be used in clinical studies after balloon dilatation, atherectomy,and laser interventions to understand the biologic changes that occur during these procedures and to determine whether intravascular ultrasound images can be used to predict the short- term and long-term results of the intervention. The intravascular ultrasound technology will also be used to assess the mechanism of restenosis following balloon angioplasty in a drug intervention trial using cilazapril, an ACE inhibitor. There will also be a long term secondary prevention trial using pravastatin, an HMG CoA reductase inhibitor, to lower serum cholesterol. Intravascular ultrasound will be used at baseline and at a 3 year follow-up period to directly measure the effect of chronic cholesterol reduction on atheroma area in human coronary arteries.